Circuit structure formed by insert molding of electric and/or optical transmission medium

ABSTRACT

A unitary circuit structure has an electric and/or optical transmission medium. The structure includes at least one of an optical signal transmission medium (22), an electric signal transmission medium (1, 8, 21, 41), and an electric power transmission medium (23) which are insert-molded in a plastic which forms a housing (7, 24) for electronic and electric devices and parts. The circuit structure serves as both conductive circuits and housing so that the electronic and electric devices and parts can be wired and mounted at high density.

BACKGROUND OF THE INVENTION

The present invention relates to a circuit structure formed byinsert-molding of electric and/or optical transmission medium inplastics. More particularly, it relates to a circuit structure whereinelectronic devices can be wired and mounted at high density.

In the conventional electronic and electric devices, electric controlsignal transmission wiring and electric power transmission wiring arecomplicated. These are large obstacles to fulfilling the strong desiresfor reduction of assembling process steps, high level functions, andminiaturization. They have been problems that cannot be solved in theconventional technology.

On the other hand, there have been many disclosures about manufacturingmethods of conductive circuit boards, including a two shot moldingmethod, a photo-additive method and a subtraction method using plating,a printed circuit transfer method, a circuit printed film fusion mappingmethod, etc. However, these methods have a great number of processingsteps, and disadvantages in heat resistance characteristics, and longterm reliability, and therefore have not developed into practical useyet.

Japanese Patent Laid-Open 58-180095, discloses a structure and a methodin which a printed-circuit board and cables are buried in plastics, andthe structure is a housing in which the usual structure having usualelectronic devices and parts implemented is fixed by plastics. However,this structure is insufficient in miniaturization and in reliability forsuch characteristics as heat resistance and thermal shock tesistance.

SUMMARY OF THE INVENTION

The present invention overcomes the difficulties mentioned above andprovides a circuit structure, wherein a conductive circuit module havingan electric and/or optical transmission medium molded to integrate inplastics and/or the transmission medium are insert-molded preferably inmaterial of a housing for electronic and electric devices preferably toserve both as conductive circuit and housing so that the electronic andelectric devices and parts can be wired and mounted at high density.

Other objects of the invention will be obvious from the contents of thespecification herein after disclosed.

The circuit structure according to the present invention is made up in away that an electric and/or optical transmission medium and an electricpower transmission medium are insert-molded to integrate in plastics. Italso can be made up to serve as housing.

A known optical fiber of glass or organic high molecular material may beused as the optical signal transmission medium.

An electric wire or lead frame of thin metal plate may be used as theelectric signal transmission medium is used an electric wire or leadframe of thin metal plate. The lead frame of thin metal plate can beobtained in a way that a thin plate of copper system, iron system,aluminum system, or superconductor material of around 0.01 to 1.0 mmthick is processed to a slit-like shape having predetermined line widthand pitch so that it has a two-dimensional or three-dimensionalstructure. A signal current flowing in the electric signal transmissionmedium is usually 8 to 50 mA. A lead frame of thin metal plate thinnerthan 0.01 mm is undesirably difficult to form without harmfuldeformation. For up to 50 mA of the current, the thickness of the leadframe of thin metal plate is sufficient to be 1 mm. Even if thethickness is made thicker than 1 mm, it will not generally provide aspecial advantage.

An electric power wire or lead frame of thick metal plate is used theelectric power transmission medium. The lead frame of thick metal platecan be obtained in a way that a thick plate of copper system or aluminumsystem material of around 0.5 to 3 mm thick is processed to atwo-dimensional or three-dimensional structure having a rectangular,elliptic, or similar cross-section. A current flowing in the electricpower transmission medium is usually 4 to 600 A. It is not preferable tomake the lead frame of thick metal plate thinner than 0.5 mm as it isnot sufficient to make the 4 A current flow. For up to 600 A of thecurrent, the thickness of the lead frame of thick metal plate issufficient to be 3 mm. Even if the thickness is made thicker than 3 mm,it will not generally provide a special advantage.

For the electric signal lead frame and the electric power lead frame, ingeneral, the above-mentioned materials may be used. However it is notnecessary to limit these materials thereto.

A high heat resistant thermosetting resin and an engineering plastics ofthermoplastic resin and a super engineering plastics having very highheat resistance can be used for the molding resin materials.

The molding method used is a new process to obtain the circuit structureuniting the conductive circuits, in a way that (1) a three-dimensionaltransmission medium or media having at least one or two different kindsof media are put in a mold, (2) parts of or whole transmission media aretransfer-molded and shaped and fixed or insulation covered at a lowpressure, and (3) the high heat resistant thermoplastic resin is madelow in viscosity and is injection-molded with the mold cavity.

While the thickness of the circuit structure according to the presentinvention has been generally 1 to 3 mm, it should be understood that itis not limited thereto.

The molding machine used is an integrated transfer and injection moldingmachine prepared for use with the present invention as shown in FIG. 4.

The thermosetting resin to be used in the transfer molding is generallyan epoxy resin containing silica. It can be replaced by an alternativephenol resin, diallyl phthalate resin, or similar filler compositethermosetting resins.

The size of the silica filler is usually around 10 to 100 μm, and itscontent is 30 to 70 wt. %. The silica can be alternatively replaced byglass fiber or similar inorganic filler.

The resin for injection molding may be dipped in a solder bath as neededfor connection as circuit module. Therefore, as the resin for injectionmolding, there can be employed the thermoplastic resins having a highheat resistance and a higher heat deflection temperature than 200° C.,such as polyphenylene sulfide (PPS), polyether sulfone (PES),polyetherimide (PEI), polysulfone (PSF), polyethylene terephthalate(PET), polyether etherketone (PEEK), polyamide (PA), polyoxymethylene(POM), acrylonitrilebutadiene styrene (ABS), and all-aromatic polyester.The PET, PA, POM, and ABS of the above-mentioned thermoplastic resinsare engineering plastics, and the other resins are super engineeringplastics.

If the shape of the transmission circuit structure is comparativelysimple, it can be molded in any of the methods, such as usual castingmethod, transfer molding method, injection molding method, and reactiveinjection molding method.

The circuit structure according to the present invention hassubstantially only the electric and/or optical signal transmissionmedium and the electric power transmission medium insert-molded tointegrate in plastics. Electronic component parts other than thetransmission media having connection terminals as necessary are mountedon the circuit structure.

The optical fiber can transmit an optical signal and the signal wire andthe lead frame of thin metal plate can transmit an electric signal, andthey provide circuit function including transmission and/or reception ofcontrol and detecting optical or electric signal. The metal conductivecircuit comprising the electric power wire and/or lead frame of thickmetal plate provides a function of transmission of electric power.

The two-dimensional or three-dimensional conductive circuit structurecan be formed in a way that a combination of one kind and any two kindsof transmission media, or a group of the three kinds of the transmissionmedia mentioned above are molded in plastics at the same time.

As described above, the conductive circuit module having thetransmission media integrated together is a new module that can performan entire operation, including control, detection, drive, of electronicand electric devices by way of transmission of the signals and electricpower. In addition, a plurality of the conductive circuit modules can beconnected with each other through the connection terminals or each ofthem can be connected to usual print circuit board or flexible printcircuit board. These features provide a great advantage that the wiringdesign of the electronic and electric devices are made at large degreesof freedom.

The circuit structure according to the present invention can be used toproduce an electronic unit in a way that integrated circuit, lightemitting diodes, capacitors, resistors, oscillators, fluorescent lights,and other similar electronic component parts are mounted therein.Mounting of the electronic component parts on the circuit structure canbe made by fitting, pressure bonding, or soldering the connectionterminals of the electronic component parts to the circuit structure. Itshould be noted that the circuit structure has connection terminals forthe connection of the external component parts.

In the prior art, wiring designs have been met by individual wiringschemes. However, this involves an inherent complicated lead wirearrangement, an increase of numbers of component parts and processsteps, low assembling efficiency, and an increase of necessary space.The present invention can solve these problems.

That is, the present invention can solve the whole problems of the priorart by improving the productivity, improving the space factor, andincreasing the design freedom. This provides an outstanding advantagethat electronic and electric devices can be miniaturized whilemaintaining high performance characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a schematic perspective view illustrating the circuitstructure in an embodiment of the present invention.

FIG. 1b is a schematic perspective view illustrating the circuitstructure of FIG. 1a with electronic component parts mounted therein.

FIG. 2a is a schematic cross-sectional view illustrating the transfermolding process in an embodiment of the present invention.

FIG. 2b is a schematic cross-sectional view illustrating the injectionmolding process in an embodiment of the present invention.

FIG. 3 is a perspective view illustrating the lead frame of thin metalplate for electric signal transmission in an embodiment of the presentinvention.

FIG. 4 is a perspective view illustrating a molding machine which canintegrate the transfer and injection moldings in forming the circuitstructure according to the present invention.

FIG. 5 is a schematic perspective view illustrating the circuitstructure of another embodiment of the present invention.

FIG. 6 is a perspective view illustrating a photosensor assembly in aprior art.

FIG. 7 is a schematic perspective view illustrating a three-dimensionalcircuit structure for a photosensor in a further embodiment of thepresent invention.

DETAILED DESCRIPTION

An optical fiber made up of usual inorganic glass or organic highmolecular material is used for the optical transmission medium. A one,two, or three dimensional lead frame obtained by processing thin plateof metal such as copper system, iron system, aluminum system, or superconductor material, to slit-like shape, or electric wire is used for thetransmission of an electric signal. An electric power wire or metalconductive circuit having a rectangular, elliptic, or similarcross-section is used for transmission of electric power.

A high heat resisting thermosetting resin such as an epoxy resin,polyimide resin, phenol resin, unsaturated polyester resin, diallylphthalate resin, or the like is used for a mold resin. A high heatresisting polyphenylene sulfide (PPS), polyethylene terephthalate (PET),polyether sulfone (PES), polyetherimide (PEI), polysulfone (PSF),polyether etherketone (PEEK), all-aromatic polyester, liquid crystalpolymer, or similar single material or its composite material with ainorganic filler, such as silica or glass fiber is used for athermoplastic resin.

In turn, a molding method is described in detail below. The moldingmethod used in this invention can be any of casting method, low pressureinjection molding method, and transfer molding method, or a two shotmolding method employing an integrated transfer and injection moldingmachine.

For the purpose of illustration only, the present invention will now beillustrated by the following embodiments. Of course, this inventionshall not be limited to the following embodiments.

In describing the preferred embodiment of the invention illustrated inthe drawings, specific terminology will be resorted to for the sake ofclarity. However, it is not intended to be limited to the specific termsso selected, and it is to be understood that each specific term includesall technical equivalents which operate in a similar manner toaccomplish a similar purpose.

EMBODIMENT 1

In the accompanying drawings, FIG. 3 is a schematic representation of athree-dimensional metal lead frame for transmitting an electric signal.A three-dimensional lead frame 1 of thin metal plate, as shown in FIG.3, is held by a supporting portion 2 of lead frame. In the figure, thelead frame 1 of thin metal plate is hatched.

The lead frame 1, as shown in FIG. 2a, is put in a mold cavity portion 4of a mold 3. Thermosetting resin 4' in FIG. 2b is transfer molded toform a module. Just after this, as shown in FIG. 2b, thermoplastic resin5 is injection-molded to form a unitary conductive circuit structureshown in FIG. 1a with the slightly opened parts of a parting plane 10 ofthe mold 3. Parts of the lead frame 1 are put at the parting plane 10shown in FIG. 2a. FIG. 2b shows the circuit structure shown in FIG. 1awith electronic component parts mounted thereon. In FIGS. 1a and 1b, thereference numeral 6 denotes a conductive circuit module, 6' a connectionterminal for the connection of an external electronic component part, 7a plastic housing, 8 a conductive circuit, 9 an electronic componentpart like a integrated circuit, and 9' an electronic component part,like a capacitor.

A molding machine such as shown in FIG. 4 is used an integrated transferand injection molding machine formed for use in the present invention.In FIG. 4, the integrated transfer and injection molding machinecomprises a transfer molding unit 11, an injection molding unit 12, amold 13, a mold clamp unit 14, a tablet heating device 15, and a controldisplay system 16.

The molding process is featured in that the electric and/or opticaltransmission medium put in the mold can be molded without anydeformation since the melted resin can be transferred at a low pressureof 3 to 9 MPa in the transfer molding. An injection molding as a secondstage is to be made for forming a two-dimensional or three-dimensionalstructure at a pressure of 0.8 to 50 times that of the transfer molding.This structure can mount different external component parts such aselectronic component parts therein. It is featured in that the resinemployed for the injection molding is able to resist a heat of at least200° C. or higher for dipping the connection parts in a solder bath. Theelectronic component parts are mounted in a circuit structure in a waythat they are connected to the transmission medium thereof by pressurebonding, dipping in a solder bath, fitting or the like.

EMBODIMENT 2

An optical fiber and lead frame of thin metal plate are used as theoptical and electric transmission media respectively; a metal conductoris used as the power transmission circuit. These are put in the mold.

A glass fiber is used for the optical fiber; a copper plate of 0.15 mmthickness is used for the lead frame of thin metal plate; and, a copperplate of 1.2 mm thick is used for the power transmission metalconductor.

In turn, using the integrated transfer and injection molding machineshown in FIG. 4, molding is made in a way similar to that of Embodiment1 described previously to obtain a unitary transmission circuit moduleas shown in FIG. 5.

In FIG. 5, the unitary transmission circuit module comprises a leadframe 21 of thin metal plate which is a transmission circuit forelectric signals, an optical fiber 22 which is a transmission circuitfor optical signals, a metal conductor 23 which is a transmissioncircuit for electric power, a plastic housing 24 of approximately 3 mmthick which is an injection-molded part, and a plastic supporter 25which is a transfer-molded part.

The resins used are epoxy resin mixed with approximately 60 wt. % ofquartz powder of approximately 80 μm size for the transfer molding andpolyphenylene sulfide (PPS) for the injection molding.

The unitary transmission circuit module provides a function of thetransmission of the optical signals and electric signals as well as afunction of the transmission of the electric power.

These electric and optical transmission functions have been heretoforeprovided by individual electric wire and optical fiber. The presentinvention can integrate those functions into one electric and opticaltransmission circuit module.

EMBODIMENT 3

The present invention is further illustrated in detail by the followingembodiment in comparison with a prior art product.

FIG. 6 shows a prior art photosensor assembly which can detect the paperfeed of a printer for use in office automation. A photosensor 31 ismounted on a bracket 32 and is connected to a connector 33 through awire bundle of usual electric wires. As this photosensor assembly usesthe wire bundle, it is not efficiently assembled, resulting in decreaseof productivity.

FIG. 7 shows a three-dimensional conductive circuit module which ismolded according to the present invention. A conductive circuit 41 ofmetal lead frame is kept inserted or buried in a molded part. Theconductive circuit 41 of metal lead frame serves as the usual wirebundle of the prior art. Electrical connection of a photosensor 43 ismade by soldering or pressure bonding. The three-dimensional circuitmodule can function with connection of an electronic or electriccircuit(s) by insertion of a connector 44.

The following describes how to form the three-dimensional conductivecircuit module. In the transfer molding as the first stage, for theelectric signal conductive circuit, a thin copper system plate of 0.1 mmthick is subjected to etching process to form slit-form conductor 41 inthe usual way, and the conductor 41 is properly bent to form athree-dimensional lead frame. The three-dimensional lead frame is put ina mold. Transfer molding is made with the epoxy resin mixed with silicafiber as in Embodiment 2 using the integrated transfer and injectionmolding machine shown in FIG. 4.

In the injection molding as the second stage, the injection molding ismade to form the three-dimensional conductive circuit module having aninjection molded plate of 2 mm thickness as shown in FIG. 7.

The module having the photosensor soldered is subjected to a reliabilitytest given in Table 1. After the test, it is guaranteed that it has noproblem. In the reliability test, the module which has no deteriorationin its drive performance is accepted.

                  TABLE 1                                                         ______________________________________                                        ITEM     TEST CONDITION        RESULT                                         ______________________________________                                        Moisture 80° C., 95% RH, 1,000 hours,                                                                 Accepted                                       resistance                                                                             5 V, 8 to 30 mA, continuous live                                     Thermal  125° C., 30 min to and fro -55° C.,                                                   Accepted                                       shock test                                                                             30 min, 300 cycles                                                   Vibration                                                                              3 G, 2 hours, in the directions                                                                     Accepted                                       resistance                                                                             of up and down, side to side,                                                 and back and forth, 10 to 50 Hz,                                              continuous live                                                      Heat     260 ± 5° C., 5 sec                                                                        Accepted                                       resistance                                                                             As per JIS C 5012                                                    for soldering                                                                 Mixed gas                                                                              H.sub.2 S, NO.sub.2, SO.sub.2 gas                                                                   Accepted                                       resistance                                                                             atmosphere of approx. 60 ppm                                                  concentration in air, 48 hours                                       ______________________________________                                    

As a result, the present invention can dissolve a problem that number ofcomponent parts is too greater, which leads to low productivity. Inother words, it accomplishes an increase of economic efficiency due tosimplified wiring and improved productivity.

With invention of the three-dimensional conductive circuit structureintegrated in resin that can transmit the optical signals, electricsignals, and electric power, the present invention provides greateconomic effects, including reduction of the number of component parts,reduction of assembling steps, and improvement of productivity. Inaddition, the present invention accomplishes the high performance andthe miniaturization of such an electronic and electric device due to theincreases of space factor, reliability, and design freedom.

It is to be understood that the form of the invention herewith shown anddescribed is to be taken as a preferred embodiment. Various changes maybe made in the shape, size and arrangement of parts. For example,equivalent elements may be substituted for those illustrated anddescribed herein, parts may be reversed, and certain features of theinvention may be utilized independently of the use of other features,all without departing from the spirit of scope of the invention asdefined in the subjoined claims.

While the principles of the invention have been described above inconnection with specific embodiments, and particular modificationsthereof, it is to be clearly understood that this description is madeonly by way of example and not as a limitation on the scope ofinvention.

What is claimed is:
 1. A circuit structure of unitary constructioncomprising a conductive circuit module having a three-dimensional shape,the circuit module consisting essentially of i) at least onetransmission medium selected from a group consisting of an opticalsignal transmission medium, an electric signal transmission medium, andan electric power transmission medium and ii) a plastic in which said atleast one transmission medium is insert-molded, wherein the opticalsignal transmission medium is composed of an optical fiber, the electricsignal transmission medium is selected from a group including anelectric wire and a lead frame of thin metal plate, and the electricpower transmission medium is selected from a group including an electricpower wire and a lead frame of thick metal plate.
 2. A circuit structureas set forth in claim 1, wherein said at least one transmission mediumcomprises the optical signal transmission medium, the electric signaltransmission medium, and the electric power transmission medium.
 3. Acircuit structure as set forth in claim 1, wherein said at least onetransmission medium comprises the electric signal transmission medium,and the electric power transmission medium.
 4. A circuit structure asset forth in claim 1, further comprising a connection terminal adaptedfor connecting the structure to an external electronic component part.5. A circuit structure as set forth in claim 1, wherein the conductivecircuit module includes at least two elements selected from the group ofan electric signal circuit, an optical signal circuit, and an electricpower transmission circuit, and an electric power transmission circuitmolded in plastics to a unitary structure and said two elements areconnected with each other through a connection terminal.
 6. A circuitstructure as set forth in claim 1, wherein the conductive circuit moduleforms a housing for electronic and electric component parts.
 7. Acircuit structure as set forth in claim 1, wherein external electroniccomponent parts are connected by a process selected from the groupincluding pressure bonding, soldering, and fitting.
 8. A circuitstructure of unitary construction comprising a conductive circuit modulehaving a three-dimensional shape, said circuit module consisting of i)at least one transmission medium selected from a group consisting of anoptical signal transmission medium, an electric signal transmissionmedium, and an electric power transmission medium and ii) a plastic inwhich said at least one transmission medium is insert-molded, whereinthe optical signal transmission medium is composed of an optical fiber,the electric signal transmission medium is selected from a groupincluding an electric wire and a lead frame of thin metal plate, and theelectric power transmission medium is selected from a group including anelectric power wire and a lead frame of thick metal plate, and wherein afunction of said circuit structure is integrated with a function ofhousing in a way that said circuit structure forms at least a part of ahousing for electronic and electric devices and parts and is connectedthrough a connection terminal to at least one device selected from thegroup including another conductive circuit, a printed circuit board, anda flexible printed circuit board to make the circuit unitary together.9. A circuit structure of unitary construction comprising conductivecircuit module having a three-dimensional shape, said circuit moduleconsisting essentially of i) at least one transmission medium selectedfrom a group consisting of an optical signal transmission medium, anelectric signal transmission medium, and an electric power transmissionmedium and ii) a plastic in which said at least one transmission mediumis insert-molded, wherein the optical signal transmission medium iscomposed of an optical fiber, the electric signal transmission medium iscomposed of a lead frame of thin metal plate, and the electric powertransmission medium is selected from a group including an electric powerwire and a lead frame of thick metal plate.
 10. A circuit structure ofunitary construction comprising a conductive circuit module having atwo-dimensional shape, the circuit module consisting essentially of i)at least one transmission medium is selected from a group consisting ofan optical signal transmission medium, an electric signal transmissionmedium, and an electric power transmission medium and ii) a plastic inwhich said at least one transmission medium is insert-molded, whereinthe optical signal transmission medium is composed of an optical fiber,the electric signal transmission medium is selected from a groupincluding an electric wire and a lead frame of thin metal plate, and theelectric power transmission medium is selected from a group including anelectric power wire and a lead frame of thick metal plate.
 11. A circuitstructure of unitary construction comprising a conductive circuit modulehaving a two-dimensional shape, said circuit module consisting of i) atleast one transmission medium is selected from a group consisting of anoptical signal transmission medium, an electric signal transmissionmedium, and an electric power transmission medium and ii) a plastic inwhich said at least one transmission medium is insert-molded, whereinthe optical signal transmission medium is composed of an optical fiber,the electric signal transmission medium is selected from a groupincluding an electric wire and a lead frame of thin metal plate, and theelectric power transmission medium is selected from a group including anelectric power wire and a lead frame of thick metal plate, and wherein afunction of said circuit structure is integrated with a function ofhousing in a way that said circuit structure forms at least a part of ahousing for electronic and electric devices and parts and is connectedthrough a connection terminal to at least one device selected from thegroup including another conductive circuit, a printed circuit board, anda flexible printed circuit board to make the circuit unitary together.12. A circuit structure of unitary construction comprising a conductivecircuit module having a two-dimensional shape, said circuit moduleconsisting essentially of i) at least one transmission medium selectedfrom a group consisting of an optical signal transmission medium, anelectric signal transmission medium, and an electric power transmissionmedium and ii) a plastic in which said at least one transmission mediumis insert-molded, wherein the optical signal transmission medium iscomposed of an optical fiber, the electric signal transmission medium iscomposed of a lead frame of thin metal plate, and the electric powertransmission medium is selected from a group including an electric powerwire and a lead frame of thick metal plate.